The present disclosure relates generally to refrigerators, and more particularly to a defrost heater system for a refrigerator.
Most refrigerators, such as that as disclosed in U.S. Pat. No. 5,711,159, include an evaporator that normally operates at sub-freezing temperatures in a compartment positioned behind the freezer compartment. A layer of frost typically builds up on the surface or coils of the evaporator. Defrost cycles are needed in order to melt any frost or ice that forms or builds upon on the refrigeration coils of the evaporator in a refrigeration system. Typical defrost systems utilize defrost heaters to melt the ice build up. The defrost heater may be similar to the heating elements on an electric stove and can be generally located near or beneath the cooling coils, which are concealed behind a panel in the refrigeration or freezer compartment. During the defrost cycle, the defrost heater gets hot. As a result of its proximity to the cooling coils, any ice or frost build-up on the coils melts. As disclosed in U.S. Pat. No. 5,042,267, filed on Oct. 5, 1990, and assigned to General Electric Company, assignee of the present invention, a radiant heater is often positioned inside a housing and below the evaporator to warm the evaporator by both convection and radiant heating in order to quickly defrost the evaporator.
However, existing radiant defrost heaters consume a significant amount of energy. Demand Side Management (DSM) is growing in importance as it has become recognized that much of the cost of generating electrical power is determined by the peak electrical power demand. The utility industry as well as the government and companies are developing strategies to limit peak electrical power demand by shifting some of the loads from high electrical power demand periods to low electrical power demand periods.
The peak energy use of an appliance such as a refrigerator typically occurs during the defrost cycle. The amount of energy that can be consumed by a refrigerator during a defrost cycle is about 500 watts. The rules agreed to by industry for DSM enabled refrigerators is that during a high electrical power demand period, the energy draw of the refrigerator should be controlled so that it is at most one-half (50%) of the peak refrigerator energy usage.
A DSM enabled refrigerator can be controlled such that a defrost cycle requested or scheduled during a high demand period is delayed. However, there are situations where a defrost cycle is initiated or started during a low demand period and is still in process when a high demand period occurs.
Once a defrost cycle is initiated, it is important to not terminate the defrost cycle until all of the frost or ice buildup has melted. If the defrost cycle is prematurely stopped while there is still a mixture of frost and water on the evaporator, this mixture will have a tendency to refreeze into solid ice. It is much more difficult to remove solid ice from an evaporator than frost. Frost tends to be more evenly distributed than solid ice and is less likely to eventually completely insulate the evaporator and reduce or block airflow. Blocked airflow will result in a service call due to lack of cooling. Thus, an incomplete or skipped defrost cycle can result in an ice-clogged evaporator. It would be advantageous to be able to safely reduce power usage in a refrigerator during a defrost cycle without risking the formation of an ice-clogged evaporator.
Accordingly, it would be desirable to provide a system that addresses at least some of the problems identified above.